This project is focused on determining how best to use sleep as an intervention to promote recovery from the biobehavioral risks posed by chronic sleep restriction. Chronic partial sleep loss due to medical conditions and social demands is common and associated with significant clinical morbidity. Our studies have shown that chronic restriction of sleep to between 4h and 6h per night results in neurobehavioral deficits that accumulate to levels equivalent to those produced by total sleep loss. We will undertake the first research to determine what aspects of sleep are critical for recuperation from the effects of chronic partial sleep loss. The issue of recovery of waking neurobehavioral and physiological functions will be addressed using an experimental approach that systematically determines the recovery potential of sleep in 180 healthy female (n=90) and male (n=90) subjects. Sleep duration will be varied parametrically on two consecutive nights, following 5 days of chronic sleep restriction. Key aspects of waking biobehavioral functions sensitive to sleep loss will be measured in subjects randomized to one of six sleep durations on recovery night 1 and one of six sleep durations on recovery night 2 (i.e., a total of 36 different combinations of sleep across the two nights). Statistically efficient response-surface modeling and dose-response regression approaches will be used for mapping recovery in neurocognitive, mood, and physiological outcomes as a function of sleep, using time in bed, total sleep time, and specific sleep physiological measures (e.g., REM sleep, slow wave energy in non- REM sleep) as independent variables. The resulting response-surface maps and dose-response curves will reveal the degree of recuperation of biobehavioral functions relative to varying amounts and types of sleep. These approaches also provide estimates of the variance attributable to gender differences, age effects, and differences in habitual sleep duration at home. The empirically estimated response-surface maps will be compared to predictions inferred from current biomathematical models of sleep-wake regulation, to assess how well these models predict recovery gained from sleep of different durations. In addition to providing the first dose-response curves for the relationship of sleep duration to recovery of waking functions, this project will explore the effects of varying sleep durations on cardiovascular markers in both women and men. The scientific data to be generated will advance theoretical understanding of sleep homeostasis; improve mathematical models of sleep-wake regulation; and inform questions of sleep need relative to public health. [unreadable] [unreadable]